avoiding compression of high-entropy data during creation of a backup of a source storage. In one example embodiment, a method for avoiding compression of high-entropy data during creation of a backup of a source storage may include identifying a chunk with an original size in a file in a source storage, compressing, during creation of a backup of the source storage, the chunk to generate a compressed chunk with a compressed size, determining a compression ratio for the chunk by comparing the original size to the compressed size, determining whether the compression ratio is less than the compression threshold, and, in response to determining that the compression ratio is less than the compression threshold, automatically designating the file as a high-entropy file and automatically avoiding compression, during the creation of the backup, of chunks in a second similar file in the source storage.
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1. A method for avoiding compression of high-entropy data during creation of a backup of a source storage, the method comprising:
identifying a chunk in a file in a source storage, the file having a file type, the chunk having an original size;
compressing, during creation of a backup of the source storage, the chunk to generate a compressed chunk, the compressed chunk having a compressed size;
determining a compression ratio for the chunk by comparing the original size to the compressed size;
determining whether the compression ratio is less than a compression threshold; and
in response to determining that the compression ratio is less than the compression threshold, automatically designating the file type as a high-entropy file type and automatically avoiding compression, during the creation of the backup, of chunks in a second file in the source storage having the file type.
12. A method for avoiding compression of high-entropy data during creation of a backup of a source storage, the method comprising:
identifying a chunk in a file in a source storage, the file having a file extension, the chunk having an original size;
compressing, during creation of a backup of the source storage, the chunk to generate a compressed chunk, the compressed chunk having a compressed size;
determining a compression ratio for the chunk by comparing the original size to the compressed size;
determining whether the compression ratio is less than a compression threshold; and
in response to determining that the compression ratio is less than the compression threshold, automatically designating the file extension as a high-entropy file extension and automatically avoiding compression, during the creation of the backup, of chunks in a second file in the source storage having the file extension.
2. The method as recited in
3. The method as recited in
4. The method as recited in
5. The method as recited in
6. The method as recited in
7. The method as recited in
in response to determining that the compression ratio is less than the compression threshold, automatically avoiding compression, during creation of the backup of the source storage, of additional chunks in the file.
8. The method as recited in
in response to determining that the compression ratio is less than the compression threshold, automatically avoiding compression, during creation of a second backup of a second source storage, of chunks in any files in the second source storage having the file type.
9. The method as recited in
the automatically designating and the automatically avoiding are further performed in response to also determining that compression ratios of a threshold number of additional chunks in one or more files in the source storage having the file type are also less than the compression threshold.
10. The method as recited in
the automatically designating and the automatically avoiding are further performed in response to also determining that compression ratios of chunks in a threshold number of additional files in the source storage having the file type are also less than the compression threshold.
11. One or more non-transitory computer-readable media storing one or more programs that are configured, when executed, to cause one or more processors to execute the method as recited in
13. The method as recited in
the backup is an image-based backup of the source storage; and
the identifying includes identifying the file to which the chunk belongs after the determining that the compression ratio is less than the compression threshold.
14. The method as recited in
15. The method as recited in
16. The method as recited in
in response to determining that the compression ratio is less than the compression threshold, automatically avoiding compression, during creation of the backup of the source storage, of additional chunks in the file.
17. The method as recited in
in response to determining that the compression ratio is less than the compression threshold, automatically avoiding compression, during creation of a second backup of a second source storage, of chunks in any files in the second source storage having the file extension.
18. The method as recited in
the automatically designating and the automatically avoiding are further performed in response to also determining that compression ratios of a threshold number of additional chunks in one or more files in the source storage having the file extension are also less than the compression threshold.
19. The method as recited in
the automatically designating and the automatically avoiding are further performed in response to also determining that compression ratios of chunks in a threshold number of additional files in the source storage having the file extension are also less than the compression threshold.
20. One or more non-transitory computer-readable media storing one or more programs that are configured, when executed, to cause one or more processors to execute the method as recited in
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The embodiments disclosed herein relate to avoiding compression of high-entropy data during creation of a backup of a source storage.
A storage is computer-readable media capable of storing data in blocks. Storages face a myriad of threats to the data they store and to their smooth and continuous operation. In order to mitigate these threats, a backup of the data in a storage may be created to represent the state of the source storage at a particular point in time and to enable the restoration of the data at some future time. Such a restoration may become desirable, for example, if the storage experiences corruption of its stored data, if the storage becomes unavailable, or if a user wishes to create a second identical storage.
A storage is typically logically divided into a finite number of fixed-length blocks. A storage also typically includes a file system which tracks the locations of the blocks that are allocated to each file that is stored in the storage. The file system also tracks the blocks that are not allocated to any file. The file system generally tracks allocated and unallocated blocks using specialized data structures, referred to as file system metadata. File system metadata is also stored in designated blocks in the storage.
Various techniques exist for backing up a source storage. One common technique involves backing up individual files stored in the source storage on a per-file basis. This technique is often referred to as file backup. File backup uses the file system of the source storage as a starting point and performs a backup by writing the files to a destination storage. Using this approach, individual files are backed up if they have been modified since the previous backup. File backup may be useful for finding and restoring a few lost or corrupted files. However, file backup may also include significant overhead in the form of bandwidth and logical overhead because file backup may require the tracking and storing of information about where each file exists within the file system of the source storage and the destination storage.
Another common technique for backing up a source storage ignores the locations of individual files stored in the source storage and instead simply backs up all allocated blocks stored in the source storage. This technique is often referred to as image backup because the backup generally contains or represents an image, or copy, of the entire allocated contents of the source storage. Using this approach, individual allocated blocks are backed up if they have been modified since the previous backup. Because image backup backs up all allocated blocks of the source storage, image backup backs up both the blocks that make up the files stored in the source storage as well as the blocks that make up the file system metadata. Also, because image backup backs up all allocated blocks rather than individual files, this approach does not generally need to be aware of the file system metadata or the files stored in the source storage, beyond utilizing minimal knowledge of the file system metadata in order to only back up allocated blocks since unallocated blocks are not generally backed up.
An image backup can be relatively fast compared to file backup because reliance on the file system is minimized. An image backup can also be relatively fast compared to a file backup because seeking is reduced. In particular, during an image backup, blocks are generally read sequentially with relatively limited seeking. In contrast, during a file backup, blocks that make up the content of individual files may be scattered, resulting in relatively extensive seeking.
One common problem that is encountered during successive file backups of a source storage or successive image backups of the source storage relates to the proliferation of backups over time. For example, where a source storage is backed up every day at 2:00 am to a destination storage, after one year 365 backups will exist for the source storage on the destination storage. This proliferation of backups can increase the amount of storage space needed to store the backups on the destination storage. This problem has been mitigated to some extent by compression schemes which are employed to compress data before storing the data in a backup, thus reducing the size of each backup and saving storage space. In particular, these compression schemes typically attempt compression on all data from a source storage that is targeted for backup. This attempted compression consumes memory and processing resources. However, these compression schemes have introduced a problem of wasted resources in source storages with high-entropy data, including data from files that already have a compressed data format such as an .MP3 file format or a .ZIP file format. The problem of wasted resources results from the memory and processing resources employed during attempts at compression of high-entropy data being wasted since high-entropy data cannot be further compressed effectively.
The subject matter claimed herein is not limited to embodiments that solve any disadvantages or that operate only in environments such as those described above. Rather, this background is only provided to illustrate one example technology area where some embodiments described herein may be practiced.
In general, example embodiments described herein relate to avoiding compression of high-entropy data during creation of a backup of a source storage. The example embodiments disclosed herein may be employed to identify a high-entropy chunk in a file in a source storage while backing up the source storage, and then later automatically avoid compression of chunks in similar files during the backup of the source storage. By identifying and automatically designating a particular file as having a high-entropy chunk, the wasting of memory and processing resources while unsuccessfully attempting to compress high-entropy chunks in similar files can be avoided.
In one example embodiment, a method for avoiding compression of high-entropy data during creation of a backup of a source storage may include identifying a chunk with an original size in a file in a source storage, compressing, during creation of a backup of the source storage, the chunk to generate a compressed chunk with a compressed size, determining a compression ratio for the chunk by comparing the original size to the compressed size, determining whether the compression ratio is less than the compression threshold, and, in response to determining that the compression ratio is less than the compression threshold, automatically designating the file as a high-entropy file and automatically avoiding compression, during the creation of the backup, of chunks in a second similar file in the source storage.
It is to be understood that both the foregoing summary and the following description of embodiments are explanatory and are not restrictive of the invention as claimed.
Example embodiments will be described and explained with additional specificity and detail through the use of the accompanying drawings in which:
The term “storage” as used herein refers to computer-readable media capable of storing data in blocks, such as one or more floppy disks, optical disks, magnetic disks, or solid state (flash) disks, or some logical portion thereof such as a volume. The term “block” as used herein refers to a fixed-length discrete sequence of bits. In some file systems, blocks are sometimes referred to as “clusters.” In some example embodiments, the size of each block may be configured to match the standard sector size of a storage on which the block is stored. For example, the size of each block may be 512 bytes (4096 bits) where 512 bytes is the size of a standard sector. In other example embodiments, the size of each block may be configured to be a multiple of the standard sector size of a storage on which the block is stored. For example, the size of each block may be 4096 bytes (32,768 bits) where 512 bytes (4096 bits) is the size of a standard sector, which results in each block including eight sectors. In some file systems, a block is the allocation unit of the file system, with the allocated blocks and free blocks being tracked by the file system. The term “allocated block” as used herein refers to a block in a storage that is currently tracked as storing data, such as file content data or metadata, by a file system of the storage. The term “free block” as used herein refers to a block in a storage that is not currently tracked as storing data, such as file content data or metadata, by a file system of the storage. The term “chunk” as used herein refers to a group of one or more blocks. The term “backup” when used herein as a noun refers to a copy or copies of one or more blocks from a storage. The term “file backup” as used herein refers to a copy or copies of one or more files from a storage. The term “image backup” as used herein refers to a backup of a storage that includes at least a copy of each unique allocated block of the storage at a point in time such that the image backup can be restored to recreate the state of the storage at the point in time. An “image backup” may also include nonunique allocated blocks and free blocks of the storage at the point in time. Example file formats for an “image backup” include the ShadowProtect Full (SPF) image backup format and the ShadowProtect Incremental (SPI) image backup format. It is understood that an “image backup” may exclude certain undesired allocated blocks such as content blocks belonging to files whose contents are not necessary for restoration purposes, such as virtual memory pagination files and machine hibernation state files.
The destination storage 110 may store one or more backups of the source storage 108. For example, the destination storage 110 may store an image backup 122 and/or a file backup 124. The image backup 122 or the file backup 124 may be restored to the restore storage 112.
Each of the systems 102, 104, and 106 may be any computing device capable of supporting a storage and communicating with other systems including, for example, file servers, web servers, personal computers, desktop computers, laptop computers, handheld devices, multiprocessor systems, microprocessor-based or programmable consumer electronics, smartphones, digital cameras, hard disk drives, flash memory drives, and virtual machines running on hypervisors. The network 120 may be any wired or wireless communication network including, for example, a Local Area Network (LAN), a Metropolitan Area Network (MAN), a Wide Area Network (WAN), a Wireless Application Protocol (WAP) network, a Bluetooth network, an Internet Protocol (IP) network such as the Internet, or some combination thereof. The network 120 may also be a network emulation of a hypervisor over which one or more virtual machines and/or physical machines may communicate.
The image backup 122 and/or file backup 124 stored in the destination storage 110 may be created by the backup module 114. For example, the backup module 114 may be one or more programs that are configured, when executed, to cause one or more processors to perform image backup operations of creating the image backup 122 of the source storage 108 and/or creating the file backup 124 of the source storage 108. It is noted that these backups may initially be created on the source system 102 and then copied to the destination system 104.
In one example embodiment, the destination system 104 may be a network server, the source system 102 may be a first desktop computer, the source storage 108 may be a volume on one or more magnetic hard drives of the first desktop computer, the restore system 106 may be a second desktop computer, the restore storage 112 may be a volume on one or more magnetic hard drives of the second desktop computer, and the network 120 may include the Internet. In this example embodiment, the first desktop computer may be configured to periodically back up the volume of the first desktop computer over the Internet to the network server as part of a backup job by creating the image backup 122 and/or the file backup 124. The second desktop computer may also be configured to restore one or more of the image backup 122 and the file backup 124 from the network server over the Internet to the volume of the second desktop computer if the first desktop computer experiences corruption of its volume or if the first desktop computer's volume becomes unavailable.
Although only a single storage is disclosed in each of the systems 102, 104, and 106 in
Having described one specific environment with respect to
As disclosed in
Each of the image backup 122 and the file backup 124 represents the state of the source storage 108 at time t(1). As disclosed in
As disclosed in
After compression of the chunks using the compression buffer 204, the image backup 122 may be created by copying the FSM from block (1) of the source storage 108 (which itself may also be compressed) and/or copying the first, second, third, and fourth compressed chunks from the compression buffer 204 into the image backup 122. Similarly, the file backup 124 may be created by copying the first compressed chunk as a compressed version of the file named “PAPER.TXT,” copying the second compressed chunk as a compressed version of the file named “SONG.MP3,” and copying the third and fourth compressed chunks as a compressed version of the file named “ARCHIVE.ZIP” into the file backup 124. However, as disclosed in
For example, a compression threshold may be determined, such as a compression threshold 214 of 2:1, and then the compression ratios of chunks compressed in the compression buffer 204 may be compared to the compression threshold 214. Where the compression ratio achieved in the compression buffer 204 is less than the compression threshold 214, resulting in wasted memory and processing resources, the file to which the chunk belongs may be determined to be a high-entropy file, and compression on similar files that are subsequently encountered can be automatically avoided to avoid subsequently wasting memory and processing resources. In this example, the compression ratios of 6:5, 4:3, and 12:11 that were achieved for each of the second, third, and fourth chunks 208, 210, and 212, respectively, are less than the compression threshold 214 of 2:1. Since the second chunk 208 belongs to the file named “SONG. MP3,” this file may be determined to be a high-entropy file, and compression of content of similar files, such as files having the same file type and/or the same “.MP3” file extension, may subsequently be automatically avoided. Similarly, since the third and fourth chunks 210 and 212 belong to the file name “ARCHIVE.ZIP,” this file may be determined to be a high-entropy file, and compression of content of similar files, such as files having the same file type and/or the same “.ZIP” file extension, may subsequently be automatically avoided.
Therefore, as disclosed in
The method 300 of
The method 300 of
The method 300 of
The method 300 of
If it is determined at decision step 308 that the compression ratio is less than the compression threshold (Yes at decision step 308), then the method 300 of
The automatically designating at step 310 may include automatically adding the file name of the file, the file type of the file, and/or the file extension of the file to a compression exclusion list. The compression exclusion list may then be checked before subsequent compression attempts to automatically avoid compression attempts on chunks from files with a matching file name, a matching file type, and/or a matching file extension, including automatically avoiding subsequent compression attempts on chunks from the same file. Therefore, it is understood that when subsequent compression attempts are avoided for “similar files,” the “similar files” may include the same file, including subsequent versions of the same file.
Further, in addition to automatically avoiding compression, at step 310, of chunks in a second similar file in the source storage, step 310 may further include automatically avoiding compression, during creation of the backup of the source storage, of additional chunks in the file. For example, due to the third chunk 210 not compressing at least as much as the compression threshold 214, the backup module 114 of
Also, the automatically avoiding compression at step 310 may further be performed during creation of a second backup of a second source storage, thereby benefiting not only backups of the source storage where the original high-entropy data was identified, but also benefiting one or more additional storages.
Further, the automatically designating and the automatically avoiding, at step 310, may further be performed in response to also determining that compression ratios of a threshold number of additional chunks in one or more files in the source storage having the same file type and/or the same file extension as the file are also less than the compression threshold, thereby potentially increasing the confidence that the high-entropy data is not only present in a single chunk of a single file, but is also consistently present in a threshold number of chunks of one or more files having the same file type and/or file extension.
Also, the automatically designating and the automatically avoiding, at step 310, may further be performed in response to also determining that compression ratios of chunks in a threshold number of additional files in the source storage having the same file type and/or the same file extension as the file are also less than the compression threshold, thereby potentially increasing the confidence that the high-entropy data is not only present in a single file, but is also consistently present in a threshold number of other files having the same file type and/or file extension.
It is understood that the identifying at step 302 may include identifying the file to which the chunk belongs after a determining at decision step 308 that the compression ratio is less than the compression threshold, since identifying the file to which the chunk belongs may not be beneficial, particularly in an image backup, if the compression ratio is not less than the compression threshold.
If it is determined at decision step 308 that the compression ratio is not less than the compression threshold (No at decision step 308), then the method 300 of
Therefore, the example method 300 disclosed herein may be employed to identify a high-entropy chunk in a file in the source storage 108 while backing up the source storage 108, and then later automatically avoid compression of chunks in similar files during the backup of the source storage 108 or during the backup of another storage. By identifying and automatically designating a particular file as having a high-entropy chunk, the wasting of memory and processing resources while unsuccessfully attempting to compress high-entropy chunks in similar files may be avoided.
It is understood that the foregoing discussion of the method 300 is but one possible implementation of a method for avoiding compression of high-entropy data during creation of a backup of a source storage, and various modifications are possible and contemplated. For example, the method 300 may be modified to combine steps 302 and 304 and/or combine steps 306 and/or 308.
Further, the method 300 may improve the functioning of a computer itself. For example, the functioning of the source system 102 (i.e., a computing device capable of supporting a storage and communicating with other systems) itself may be improved by the method 300 at least because the creation of the backup of the source storage 108 of the source system 102 during the method 300 may enable the restoration of the source storage 108 if, for example, the source storage 108 experiences corruption of its stored data, the source storage 108 becomes unavailable, or a user wishes to create a second identical or virtual source storage 108. Also, the method 300 may improve the technical field of backup and disaster recovery (BDR). For example, the technical field of BDR may be improved by the method 300 at least because prior art backup methods for the source storage 108 did not enable a user to avoid compression of high-entropy chunks by automatically designating a particular file as a high-entropy file and automatically avoiding compression of subsequent similar files, whereas the method 300 may be employed to automatically designate a high-entropy file and automatically avoid compression of subsequent similar files.
The embodiments described herein may include the use of a special-purpose or general-purpose computer, including various computer hardware or software modules, as discussed in greater detail below.
Embodiments described herein may be implemented using non-transitory computer-readable media for carrying or having computer-executable instructions or data structures stored thereon. Such computer-readable media may be any available media that may be accessed by a general-purpose or special-purpose computer. By way of example, and not limitation, such computer-readable media may include non-transitory computer-readable storage media including RAM, ROM, EEPROM, CD-ROM or other optical disk storage, magnetic disk storage or other magnetic storage devices, or any other storage medium which may be used to carry or store one or more desired programs having program code in the form of computer-executable instructions or data structures and which may be accessed and executed by a general-purpose computer, special-purpose computer, or virtual computer such as a virtual machine. Combinations of the above may also be included within the scope of computer-readable media.
Computer-executable instructions comprise, for example, instructions and data which, when executed by one or more processors, cause a general-purpose computer, special-purpose computer, or virtual computer such as a virtual machine to perform a certain method, function, or group of methods or functions. Although the subject matter has been described in language specific to structural features and/or methodological steps, it is to be understood that the subject matter defined in the appended claims is not necessarily limited to the specific features or steps described above. Rather, the specific features and steps described above are disclosed as example forms of implementing the claims.
As used herein, the term “module” may refer to software objects or routines that execute on a computing system. The different modules described herein may be implemented as objects or processes that execute on a computing system (e.g., as separate threads). While the system and methods described herein are preferably implemented in software, implementations in hardware or a combination of software and hardware are also possible and contemplated.
All examples and conditional language recited herein are intended for pedagogical objects to aid the reader in understanding the example embodiments and the concepts contributed by the inventor to furthering the art, and are to be construed as being without limitation to such specifically-recited examples and conditions.
Williams, Stephen, Bushman, Nathan S.
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